JP2537767B2 - Optical recording / reproducing device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an optical recording / reproducing apparatus including a head block having an optical head for optically recording information on a disc-shaped record carrier and reproducing information recorded on the disc-shaped record carrier. In particular, optical recording capable of following a minute spot of light from the optical head built in the head block to the warp, unevenness, eccentricity of the disk-shaped record carrier and constant-speed feed of the head block itself. It is to provide a reproducing apparatus.

Generally, in an optical recording / reproducing apparatus having a head block having an optical head for optically recording information on a disc-shaped record carrier or reproducing information recorded on the disc-shaped record carrier, several disc-shaped record carriers are used. In order to record a minute pit of about μm as information or to reproduce a minute pit recorded as information, a minute spot of light from the optical head is made to follow the warp or unevenness of the disk-shaped recording medium, or track deviation due to eccentricity. There is a need. In addition, it is necessary to move a minute spot for the steady feed of the head block.

1 and 2 show a conventional optical recording / reproducing apparatus. In FIGS. 1 and 2, 1 is an objective lens, 2 is a voice coil, 3 is a magnetic circuit, 4 is a head block, and 5 is a head block. Is a tracking mirror, 6 is an actuator,
7 is a feed motor, 8 is a feed screw, 9 is a feed nut, 10 is a semiconductor laser, 11 is a collimator lens, 12 is a half mirror, 13 is a detection lens, 14 is an optical detector, 15 is a guide rail, and 16 is a disc motor. , 17 is a disk-shaped record carrier, 18
Is a record carrier mounting device.

In the optical recording / reproducing apparatus configured as described above, regarding the warp and unevenness of the disk-shaped record carrier, the objective lens 1 is perpendicular to the disk-shaped record carrier 17 by the voice coil 2 and the magnetic circuit 3 fixed to the head block 4. Driven in the direction (arrow a), servo is applied so as to follow the warp and the unevenness. Regarding the eccentricity, the tracking mirror 5 is fixed to the actuator 6 so as to rotate and vibrate (arrow b),
By tilting the optical axis and making it enter the objective lens 1, servo is applied so that the minute spot of light follows the eccentricity. Further, as another means, there is known one in which the objective lens 1 is driven not only in the direction perpendicular to the disk-shaped record carrier but also in the radial direction of the disk-shaped record carrier so that the minute spot of light follows the eccentricity. Has been. Further, regarding the steady feed, the head block 4 is moved by the feed motor 7, the feed screw 8 directly connected to the feed motor 7, and the feed nut 9 fixed to the head block 4. As another means, a head block is also known to be sent by a rack and a pinion.

However, in the above-mentioned optical recording / reproducing apparatus, the head block 4 has to be mounted with the drive magnetic circuit 3 of the objective lens 1, the drive actuator 6 of the tracking mirror 5, and the like, which makes the head block 4 heavy and large in shape. In particular, if the diameter of the driving magnetic circuit 3 of the objective lens 1 is large, the diameter of the outermost circumference which can be recorded or reproduced by contacting the disk motor 16 becomes large, resulting in a loss of recording time. In addition, the feed guide 15 and the feed screw 8
(Or rack or pinion) is required, and the speed of steady feed and the speed of fast feed are required to have a speed ratio of 100 to 1000 times. Therefore, it is possible to obtain that speed ratio only by controlling the rotation speed of the feed motor 7. This is impossible, and gear shift or the like must be used, which is very complicated and expensive. Further, in the optical system, the movement of the objective lens 1 and the rotation of the tracking mirror 5 change the length and inclination of the optical axis, which causes a problem that the design of the optical system becomes very difficult.

The present invention solves the above-mentioned conventional drawbacks by forming a head block having an optical head in the form of an arm, and the arm-shaped head block is used as a disc-shaped record carrier with its own center of gravity as a fulcrum. In contrast, vertical direction (focus direction) and horizontal direction (tracking direction)
Are rotatably supported in two directions, generate a couple centered on the fulcrum, and are driven in two directions, a vertical direction and a parallel direction, with respect to the disc-shaped record carrier.

Examples of the optical recording / reproducing apparatus of the present invention will be described below. 3 to 5 show an embodiment of the optical recording / reproducing apparatus of the present invention. In FIGS. 3 to 5, the objective lens 1, the semiconductor laser 10, the collimator lens 11,
An optical head including a half mirror 12, a detection lens 13, a photodetector 14 and the like is housed in an arm-shaped head block 19. This optical head comprises means for condensing light (semiconductor laser 10, collimator lens 11, objective lens 1) and means for detecting information (half mirror 12, detection lens 13, photodetector 14). still,
A fixed mirror 21 is used to configure the head block 19 into an arm shape. The objective lens 1 is directly attached to the tip of the arm-shaped head block 19. And
The arm-shaped head block 19 is rotatably supported at its own center of gravity with respect to the disk-shaped record carrier 17 in two directions, a vertical direction (focusing direction) and a horizontal direction (tracking direction). A pivot bearing 22 supports the arm-shaped head block 19 so as to rotate in a plane perpendicular to the recording surface. Reference numeral 23 denotes a rolling bearing, which is inserted between a vertical shaft 20 supporting the head block 19 by a pivot shaft 22 and a center hole of a cylindrical magnet 27 described later, and the arm-shaped head block 19 is parallel to the record carrier surface. It is supported to rotate. The center of rotation of these is the arm-shaped head block 19
The fulcrum is aligned with the center of gravity of the optical head. Further, a rotary shaft 20 (the arm-shaped head block 19 moves parallel to the recording surface) perpendicular to the disk-shaped record carrier is concentric X-.
As X ', the cylindrical bobbin 24 has an arm-shaped head block 19
It is fixed to. Two kinds of coils 25, 26 are wound around the cylindrical bobbin 24. How to wind these coils will be described later. Then, the right-angled rotary shaft 20 is concentric X-
A cylindrical gap is formed by the cylindrical magnet 27 and the cylindrical yoke 28 designated as X ', and the above coil is inserted in the gap with a clearance. The magnetic pole direction of the cylindrical magnet 27 is magnetized in the diametrical direction. The cylindrical gap in the direction perpendicular to the magnetization direction may have a larger gap in that portion as shown in FIGS. 3 and 5.

Now, how to wind the coils 25 and 26 will be described. First, the fifth
In the figure, consider an angle coordinate system centered on XX 'and consider in a development view in which the direction perpendicular to the magnetic pole direction is θ = 0.
Figure 6 shows this. One rotation is shown from θ = 0 to θ−360 °. FIG. 6 (b) shows the magnetic flux density. When θ = 0, the magnetic flux is 0, and when θ = 90 °, the maximum magnetic flux is obtained. When θ = 180 °, the magnetic flux is 0 and θ = 270 °, and the maximum magnetic flux is again (however, the direction is different, so the direction). Then, it becomes 0 again at 360 °,
Return to the original. The gap in the direction perpendicular to the magnetic pole direction is partially increased by widening the portion (A) where the magnetic flux density is small at θ = 0 and 180 °, and the magnetic flux density is large at θ = 90 ° and 270 °. This is to widen the portion (B). FIG. 6 is a development view of the coils 25 and 26 wound around the bobbin 24. The tracking drive coil 25 is wound in a straight line on the development view from the lower end a point of the bobbin 24 to the position b point at the upper end of the bobbin 24, which is shifted by 180 °. Wrap toward the next position d (C is the same point), then rewind again at the second point and wind toward the position e shifted 180 ° at the upper end, that is, the position next to the coil thickness at the second point e By returning to that point and continuing this winding work, the winding of the coil will end at the position of the final coil. In this way, the coils of the solid line group in the figure are wound. Also, starting from the lower end a ′ on the opposite side of the lower end a, in the opposite direction to the solid line group, exactly the same as
There are coils of dotted line group ending in “H”, “D”, “H”, “H”, “T” ... and the last S, and these are connected in series or in parallel to form a tracking drive coil. . If an electrode is connected to the points a and a'and an electrode is connected to the soot ', a current flows in the direction of the arrow shown parallel to the coil,
According to Framing's left-hand rule, a force acts on the coils of the solid line group in the directions of solid arrows C and C ′, and a force of the coils in the dotted line group acts in the directions of dotted arrows D and D ′. Therefore, the component force becomes E, E ', and they point in the same direction. Therefore, a couple of force is generated around the axis XX ′, and the arm-shaped head block 19 rotates in the direction parallel to the disc-shaped record carrier 17. Therefore, when a tracking control current detected by the optical system in the head block 19 is applied to the tracking drive coil 25, the arm-shaped head block 19 oscillates rotationally and a minute spot follows the recording track while tracking it. Therefore, it is not necessary to add feed control newly. The focus servo drive coil 26 is wound in parallel along the circumference of the bobbin 24. When a current is applied to this, a force is generated in the directions of the arrows F and F '. Since the forces of opposite directions are generated at θ = 90 ° and θ == 270 °, a couple of forces are generated around the axis Y-Y ′, and the arm-shaped head block 19 is perpendicular to the disc-shaped record carrier. Rotate to. When a focus control current detected by the optical system in the head block 19 is applied to the focus servo drive coil 26, the arm-shaped head block 19 oscillates rotationally and follows the irregularities and the warp of the disk-shaped record carrier.

As described above, according to the present invention, the optical system for signal detection is built in the arm-shaped head block, and the head block is supported so as to be rotatable in the two directions of the vertical direction and the parallel direction with respect to the disk-shaped record carrier. However, since two types of coils are wound in one magnetic circuit, it is not necessary to provide a drive unit in the head block, so that the weight and the size can be reduced. In addition, since there is no change in the length of the optical axis and no change in the inclination of the optical axis in the optical system, it is easy to design the optical system. Also, since the center of gravity of the head block is the fulcrum of rotation, gravity and external vibrations act on the center of gravity, so there is no rotational moment to rotate the arm-shaped head block, and it is possible to use it in any vertical or inverted posture. Also, an optical head that is resistant to external vibration can be configured. Further, since the head block does not move in a flat motion but in a rotary motion, the equivalent mass in the drive unit can be made very light. Therefore, focus servo and tracking servo can be performed by driving the head block in two directions, a vertical direction and a parallel direction with respect to the record carrier. Moreover, since tracking is performed while moving the head block, there is no need for a device for feeding the head block with screws, rack and pinion, etc. and their control system, and there is an advantage that a very low cost detection servo system can be constructed. Is.

[Brief description of drawings]

FIG. 1 is a plan view of a conventional optical recording / reproducing apparatus, FIG. 2 is a front view of the apparatus, FIG. 3 is a plan view showing an embodiment of the optical recording / reproducing apparatus of the present invention, and FIG. FIG. 5 is a front view of the apparatus, FIG. 5 is an exploded perspective view of the drive section of the apparatus, FIG. 6 shows a coil of the drive section of the apparatus, a is its developed view, and b is its magnetic flux density distribution diagram. 1 ... Objective lens, 10 ... Semiconductor laser, 11 ... Collimator lens, 12 ... Half mirror, 13 ... Detection lens, 14 ... Photodetector, 17 ... Record carrier, 19 ... Head block, 20 …… Rotary axis, 21 …… Fixed mirror, 22 ……
Pivot bearing, 23 …… Rolling bearing, 24 …… Cylinder bobbin, 25 …… Tracking drive coil, 26 …… Focus servo drive coil, 27 …… Cylinder magnet, 28 …… Cylinder yoke.

Continuation of front page (56) Reference JP-A-56-119946 (JP, A) JP-A-51-35309 (JP, A) JP-A-50-44803 (JP, A)

Claims (2)

(57) [Claims] 1. An optical head including an objective lens, a semiconductor laser, a photodetector and a half mirror, which is an optical head for optically recording information on a disk-shaped record carrier or reproducing information recorded on the disk-shaped record carrier. An optical head is constructed by fixing system parts in an arm-shaped head block, and the arm block is used as a fulcrum for the center of gravity of the head block, and is perpendicular to the record carrier (focus direction).
And a supporting means for rotatably supporting in two directions of a parallel direction (tracking direction) and a force centering on a fulcrum of the head block, so that the head block is perpendicular and parallel to the record carrier. An optical recording / reproducing apparatus comprising an electromagnetic driving means for driving in two directions. 2. An electromagnetic drive means for driving a head block is arranged outside the head block and is magnetized in a concentric diametrical direction about an axis about which the head block rotates in a direction parallel to the recording medium. Forming a cylindrical gap between the magnet and the cylindrical yoke, and winding a first coil parallel to the circumference of a cylindrical bobbin provided on the head block around the fulcrum of the head block, and The optical system according to claim 1, characterized in that a second coil is wound around the upper end different from the lower end by 180 ° and from the upper end to the lower end, and is inserted into the cylindrical gap with a clearance. Recording / playback device.